Operational Study of a Phosphoric Acid Fuel Cell with Methanol/Steam Reforming

Studies were performed comparing the operation of phosphoric acid fuel cells on hydrogen and air at constant load as a function of time and after operation under other conditions, namely: (i) periodic direct injection of methanol-water vapor, simulating failure of the steam reforming unit, and (ii) open-circuit excursion. Tests were carried out on two 3W fuel cells (Energy Research Corporation, Danbury, Connecticut). Detailed organic product analyses of condensed effluent gases of both anode and cathode reveals that trimethylphosphate, a suspect carcinogenic compound, is released. After 5-6h, direct addition of methanol/water vapor at a rate sufficient to support constant 200–100 mA/cm² performance on hydrogen (steam re-former unit assumed 90% conversion) 0.5 mg of trimethylphosphate were detected from both anode and cathode effluents. These results translate into about 10–30 ppm/h of trimethylphosphate in the anode effluent and about one-third or less of that amount in the cathode effluent stream. These results may impact in situ methanol reforming in phosphoric acid fuel cells and also external reforming at low methanol steam reforming conversion.